Kuhs, Werner F.

[["dc.bibliographiccitation.firstpage","4295"],["dc.bibliographiccitation.issue","17"],["dc.bibliographiccitation.journal","The Journal of Physical Chemistry Letters"],["dc.bibliographiccitation.lastpage","4299"],["dc.bibliographiccitation.volume","8"],["dc.contributor.author","Amos, Daniel M."],["dc.contributor.author","Donnelly, Mary-Ellen"],["dc.contributor.author","Teeratchanan, Pattanasak"],["dc.contributor.author","Bull, Craig L."],["dc.contributor.author","Falenty, Andrzej"],["dc.contributor.author","Kuhs, Werner F."],["dc.contributor.author","Hermann, Andreas"],["dc.contributor.author","Loveday, John S."],["dc.date.accessioned","2020-12-10T15:22:46Z"],["dc.date.available","2020-12-10T15:22:46Z"],["dc.date.issued","2017"],["dc.identifier.doi","10.1021/acs.jpclett.7b01787"],["dc.identifier.issn","1948-7185"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/16715"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/73532"],["dc.language.iso","en"],["dc.notes.intern","DOI Import GROB-354"],["dc.notes.intern","Merged from goescholar"],["dc.rights","Goescholar"],["dc.rights.uri","https://goescholar.uni-goettingen.de/licenses"],["dc.title","A Chiral Gas–Hydrate Structure Common to the Carbon Dioxide–Water and Hydrogen–Water Systems"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","6275"],["dc.bibliographiccitation.issue","10"],["dc.bibliographiccitation.journal","Energy & Fuels"],["dc.bibliographiccitation.lastpage","6283"],["dc.bibliographiccitation.volume","28"],["dc.contributor.author","Falenty, Andrzej"],["dc.contributor.author","Kuhs, Werner F."],["dc.contributor.author","Glockzin, Michael"],["dc.contributor.author","Rehder, Gregor"],["dc.date.accessioned","2018-11-07T09:34:23Z"],["dc.date.available","2018-11-07T09:34:23Z"],["dc.date.issued","2014"],["dc.description.abstract","Self-preservation is a kinetic anomaly that allows for storing a substantial amount of gas locked in gas hydrate far outside its thermodynamic stability field for a period of days, weeks, or even months under very mild pressuretemperature (pT) conditions, by merely maintaining temperatures below the melting point of ice. Utilizing this phenomenon for low-cost storage and transportation of natural gas is not yet sufficiently developed to be competitive with already existing, well-established methods (e.g., liquefied natural gas (LNG), gas to liquid (GTL), compressed natural gas (CNG), or pipeline (PL)). Aside from the refinement of numerous engineering and safety aspects, a deeper understanding of the self-preservation phenomenon is needed in order to promote these technologies. We address some of these outstanding issues in a series of isothermalisobaric pressurevolumetemperature (pVT) experiments exploring the kinetics of the dissociation of pure sI methane hydrate to ice and CH4 gas in a wide pT field applicable to gas-hydrate-based technologies. By means of ex situ cryo-SEM, we correlate the kinetic data with the morphology of initially formed ice coatings recovered at various stages of the transformation. The pT dependence of the self-preservation strength is seen as a complex interplay between (1) ice microstructures (shape, arrangement, and size of ice crystals) and (2) annealing rate of the ice coating that acts as a diffusion barrier for escaping gas. Moreover, we recognize a progressive sintering of ice coatings of individual particles when close to the melting point of ice. The optimal conditions for the transport and storage at ambient pressure, where this issue is minimized and the preservation strength is still very high, have been found at similar to 250 K. Further fine-tuning of the storage capacity may involve elevating the storage pressure and active temperature control."],["dc.description.sponsorship","German Federal Ministry of Economics and Technology (BMWi) [03SX250J]"],["dc.identifier.doi","10.1021/ef501409g"],["dc.identifier.isi","000343336000011"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/32160"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Chemical Soc"],["dc.relation.issn","1520-5029"],["dc.relation.issn","0887-0624"],["dc.title","\"Self-Preservation\" of CH4 Hydrates for Gas Transport Technology: Pressure-Temperature Dependence and Ice Microstructures"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","27159"],["dc.bibliographiccitation.issue","48"],["dc.bibliographiccitation.journal","The Journal of Physical Chemistry C"],["dc.bibliographiccitation.lastpage","27172"],["dc.bibliographiccitation.volume","120"],["dc.contributor.author","Falenty, A."],["dc.contributor.author","Qin, Jian-Chun"],["dc.contributor.author","Salamatin, Andrey N."],["dc.contributor.author","Yang, L."],["dc.contributor.author","Kuhs, Werner F."],["dc.date.accessioned","2018-11-07T10:04:36Z"],["dc.date.available","2018-11-07T10:04:36Z"],["dc.date.issued","2016"],["dc.description.abstract","The exchange process between CO2 and methane hydrate has been observed in numerous laboratory experiments, computer simulations, and recently confirmed in a field test. Yet, to date there is no kinetic model capable of accurately predicting the swapping process at given fluid composition and p-T conditions. Major obstacles on the way to an adequate mathematical description are caused by the insufficient characterization of experimental environments and a nearly complete lack of information on the time-resolved composition of the two-phase fluid at the gas hydrate interface. Here we show that all necessary data can be provided by a combination of cryo-SEM, Raman, and neutron diffraction measurements that deliver accurate space-averaged, time-resolved in situ data on the CH4-CO2 exchange reactions at conditions relevant to sedimentary matrixes of continental margins. Results from diffraction are cross-correlated with ex situ Raman spectroscopy to provide reliable information on the preferential sites for CO2 and CH4 in the (partially) exchanged hydrate. We also show a novel approach based on scattering of neutrons to probe the fluid composition during the in situ replacement in a time-resolved, noninvasive manner. The replacement is seen as a two-step process including (1) a fast surface reaction parallel to a fast enrichment of the surrounding fluid phase with CH4 followed by (2) a much slower permeation-limited gas swapping between the gas hydrate and mixed ambient CH4-CO2 fluid. The main part of the replacement reaction takes place in the second stage. Based on our earlier experimental studies and existing literature we work toward a quantitative gas exchange model which elaborates the hole-in-cage-wall diffusion mechanism to describe the two-component gas replacement."],["dc.identifier.doi","10.1021/acs.jpcc.6b09460"],["dc.identifier.isi","000389624400009"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/38730"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Chemical Soc"],["dc.relation.issn","1932-7447"],["dc.title","Fluid Composition and Kinetics of the in Situ Replacement in CH4-CO2 Hydrate System"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","231"],["dc.bibliographiccitation.issue","7530"],["dc.bibliographiccitation.journal","Nature"],["dc.bibliographiccitation.lastpage","+"],["dc.bibliographiccitation.volume","516"],["dc.contributor.author","Falenty, Andrzej"],["dc.contributor.author","Hansen, Thomas C."],["dc.contributor.author","Kuhs, Werner F."],["dc.date.accessioned","2018-11-07T09:31:19Z"],["dc.date.available","2018-11-07T09:31:19Z"],["dc.date.issued","2014"],["dc.description.abstract","Gas hydrates are ice-like solids, in which guest molecules or atoms are trapped inside cages formed within a crystalline host framework (clathrate) of hydrogen-bonded water molecules(1). They are naturally present in large quantities on the deep ocean floor and as permafrost, can form in and block gas pipelines, and are thought to occur widely on Earth and beyond. A natural point of reference for this large and ubiquitous family of inclusion compounds is the empty hydrate lattice(1-6), which is usually regarded as experimentally inaccessible because the guest species stabilize the host framework. However, it has been suggested that sufficiently small guests may be removed to leave behind metastable empty clathrates(7,8), and guest-free Si-and Ge-clathrates have indeed been obtained(9,10). Here we show that this strategy can also be applied to water-based clathrates: five days of continuous vacuum pumping on small particles of neon hydrate (of structure sII) removes all guests, allowing us to determine the crystal structure, thermal expansivity and limit of metastability of the empty hydrate. It is the seventeenth experimentally established crystalline ice phase(11), ice XVI according to the current ice nomenclature, has a density of 0.81 grams per cubic centimetre (making it the least dense of all known crystalline water phases) and is expected(7,12) to be the stable low-temperature phase of water at negative pressures (that is, under tension). We find that the empty hydrate structure exhibits negative thermal expansion below about 55 kelvin, and that it is mechanically more stable and has at low temperatures larger lattice constants than the filled hydrate. These observations attest to the importance of kinetic effects and host-guest interactions in clathrate hydrates, with further characterization of the empty hydrate expected to improve our understanding of the structure, properties and behaviour of these unique materials."],["dc.description.sponsorship","Bundesministeriums fur Bildung und Forschung (BMBF)"],["dc.identifier.doi","10.1038/nature14014"],["dc.identifier.isi","000346383500041"],["dc.identifier.pmid","25503235"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/31515"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Nature Publishing Group"],["dc.relation.issn","1476-4687"],["dc.relation.issn","0028-0836"],["dc.title","Formation and properties of ice XVI obtained by emptying a type sII clathrate hydrate"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","17603"],["dc.bibliographiccitation.issue","33"],["dc.bibliographiccitation.journal","The Journal of Physical Chemistry C"],["dc.bibliographiccitation.lastpage","17616"],["dc.bibliographiccitation.volume","121"],["dc.contributor.author","Salamatin, A. N."],["dc.contributor.author","Falenty, A."],["dc.contributor.author","Kuhs, W. F."],["dc.date.accessioned","2020-12-10T15:22:44Z"],["dc.date.available","2020-12-10T15:22:44Z"],["dc.date.issued","2017"],["dc.identifier.doi","10.1021/acs.jpcc.7b04391"],["dc.identifier.eissn","1932-7455"],["dc.identifier.issn","1932-7447"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/73517"],["dc.language.iso","en"],["dc.notes.intern","DOI Import GROB-354"],["dc.title","Diffusion Model for Gas Replacement in an Isostructural CH 4 –CO 2 Hydrate System"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1711"],["dc.bibliographiccitation.issue","6"],["dc.bibliographiccitation.journal","Geochemistry Geophysics Geosystems"],["dc.bibliographiccitation.lastpage","1722"],["dc.bibliographiccitation.volume","16"],["dc.contributor.author","Chaouachi, Marwen"],["dc.contributor.author","Falenty, Andrzej"],["dc.contributor.author","Sell, Kathleen"],["dc.contributor.author","Enzmann, Frieder"],["dc.contributor.author","Kersten, Michael"],["dc.contributor.author","Haberthuer, David"],["dc.contributor.author","Kuhs, Werner F."],["dc.date.accessioned","2018-11-07T09:56:17Z"],["dc.date.available","2018-11-07T09:56:17Z"],["dc.date.issued","2015"],["dc.description.abstract","The formation process of gas hydrates in sedimentary matrices is of crucial importance for the physical and transport properties of the resulting aggregates. This process has never been observed in situ at submicron resolution. Here we report on synchrotron-based microtomographic studies by which the nucleation and growth processes of gas hydrate were observed at 276 K in various sedimentary matrices such as natural quartz (with and without admixtures of montmorillonite type clay) or glass beads with different surface properties, at varying water saturation. Both juvenile water and metastably gas-enriched water obtained from gas hydrate decomposition was used. Xenon gas was employed to enhance the density contrast between gas hydrate and the fluid phases involved. The nucleation sites can be easily identified and the various growth patterns are clearly established. In sediments under-saturated with juvenile water, nucleation starts at the water-gas interface resulting in an initially several micrometer thick gas hydrate film; further growth proceeds to form isometric single crystals of 10-20 mu m size. The growth of gas hydrate from gas-enriched water follows a different pattern, via the nucleation in the bulk of liquid producing polyhedral single crystals. A striking feature in both cases is the systematic appearance of a fluid phase film of up to several micron thickness between gas hydrates and the surface of the quartz grains. These microstructural findings are relevant for future efforts of quantitative rock physics modeling of gas hydrates in sedimentary matrices and explain the anomalous attenuation of seismic/sonic waves."],["dc.identifier.doi","10.1002/2015GC005811"],["dc.identifier.isi","000358007800002"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/36928"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Geophysical Union"],["dc.relation.issn","1525-2027"],["dc.title","Microstructural evolution of gas hydrates in sedimentary matrices observed with synchrotron X-ray computed tomographic microscopy"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","11159"],["dc.bibliographiccitation.issue","20"],["dc.bibliographiccitation.journal","The Journal of Physical Chemistry C"],["dc.bibliographiccitation.lastpage","11166"],["dc.bibliographiccitation.volume","122"],["dc.contributor.author","Schaack, Sofiane"],["dc.contributor.author","Ranieri, Umbertoluca"],["dc.contributor.author","Depondt, Philippe"],["dc.contributor.author","Gaal, Richard"],["dc.contributor.author","Kuhs, Werner F."],["dc.contributor.author","Falenty, Andrzej"],["dc.contributor.author","Gillet, Philippe"],["dc.contributor.author","Finocchi, Fabio"],["dc.contributor.author","Bove, Livia E."],["dc.date.accessioned","2020-12-10T15:22:45Z"],["dc.date.available","2020-12-10T15:22:45Z"],["dc.date.issued","2018"],["dc.identifier.doi","10.1021/acs.jpcc.8b02783"],["dc.identifier.eissn","1932-7455"],["dc.identifier.issn","1932-7447"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/73524"],["dc.language.iso","en"],["dc.notes.intern","DOI Import GROB-354"],["dc.title","Orientational Ordering, Locking-in, and Distortion of CH 4 Molecules in Methane Hydrate III under High Pressure"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","s415"],["dc.bibliographiccitation.issue","a1"],["dc.bibliographiccitation.journal","Acta Crystallographica Section A Foundations and Advances"],["dc.bibliographiccitation.lastpage","s415"],["dc.bibliographiccitation.volume","72"],["dc.contributor.author","Ranieri, Umbertoluca"],["dc.contributor.author","Bove, Livia E."],["dc.contributor.author","Klotz, Stefan"],["dc.contributor.author","Hansen, Thomas C."],["dc.contributor.author","Koza, Michael M."],["dc.contributor.author","Gillet, Philippe"],["dc.contributor.author","Wallacher, Dirk"],["dc.contributor.author","Falenty, Andrzej"],["dc.contributor.author","Kuhs, Werner F."],["dc.date.accessioned","2020-12-10T18:26:01Z"],["dc.date.available","2020-12-10T18:26:01Z"],["dc.date.issued","2016"],["dc.identifier.doi","10.1107/S205327331609392X"],["dc.identifier.issn","2053-2733"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/75917"],["dc.notes.intern","DOI Import GROB-354"],["dc.title","Neutron diffraction on methane and hydrogen hydrates under high pressure"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","4022"],["dc.bibliographiccitation.issue","10"],["dc.bibliographiccitation.journal","The Journal of Physical Chemistry C"],["dc.bibliographiccitation.lastpage","4032"],["dc.bibliographiccitation.volume","115"],["dc.contributor.author","Falenty, Andrzej"],["dc.contributor.author","Genov, Georgi"],["dc.contributor.author","Hansen, Thomas C."],["dc.contributor.author","Kuhs, Werner F."],["dc.contributor.author","Salamatin, Andrey N."],["dc.date.accessioned","2018-11-07T08:58:05Z"],["dc.date.available","2018-11-07T08:58:05Z"],["dc.date.issued","2011"],["dc.description.abstract","The gas hydrate growth from frostlike powders composed of micrometer-sized ice particles does not start with hydrate shell formation, because the initial hydrate film thickness established in earlier work exceeds the ice particle dimensions. In this limiting case, the ice, grains are directly consumed by a growing nucleus created on the particle surface. The conventional Johnson-Mehl-Avrami-Kolmogorov (JM-AK) model,(1) which considers (re-) crystallization reactions phenomenologically in terms of the constituent nucleation and subsequent growth processes, cannot be directly applied to the hydrate formation from frost due to the assumption of an infinitely large domain of crystallization. We present here a modified approach to account for the small particle sizes of the starting material and extend the existing theory of gas hydrate formation from monodisperse ice powders(3-5) to the low-temperature and low-ice-particle-size limit. This approach may also prove to be very useful for applying chemical reactions starting on the surface of nanomaterials. In situ neutron scattering was used to obtain the experimental degree of transformation as a function of temperature between 185 and 195 K. The data were analyzed with the modified JMAK model constrained by information from cryo-SEM and BET measurements. Based on the obtained activation energies for hydrate nucleation and growth, an estimate is given for the probability of formation of CO2 hydrates at conditions relevant for Mars; a direct reaction of CO2 gas with water frost is considered to be very unlikely on the Martian surface under current conditions."],["dc.identifier.doi","10.1021/jp1084229"],["dc.identifier.isi","000288113400026"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/23558"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Chemical Soc"],["dc.relation.issn","1932-7447"],["dc.title","Kinetics of CO2 Hydrate Formation from Water Frost at Low Temperatures: Experimental Results and Theoretical Model"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","15975"],["dc.bibliographiccitation.issue","49"],["dc.bibliographiccitation.journal","The Journal of Physical Chemistry B"],["dc.bibliographiccitation.lastpage","15988"],["dc.bibliographiccitation.volume","113"],["dc.contributor.author","Falenty, Andrzej"],["dc.contributor.author","Kuhs, Werner F."],["dc.date.accessioned","2018-11-07T11:21:07Z"],["dc.date.available","2018-11-07T11:21:07Z"],["dc.date.issued","2009"],["dc.description.abstract","Gas hydrates can exhibit an anomalously slow decomposition outside their thermodynamic stability field; the phenomenon is called \"self-preservation\" and is mostly studied at ambient pressure and at temperatures between similar to 240 K and the melting point of ice. Here, we present a combination of in situ neutron diffraction studies, pVT work, and ex situ scanning electron microscopy (SEM) on CO2 clathrates covering a much broader p-T field, stretching from 200 to 270 K and pressures between the hydrate stability limit and 0.6 kPa (6 mbar), a pressure far outside stability. The self-preservation regime above 240 K is confirmed over a broad pressure range and appears to be caused by the annealing of an ice cover formed in the initial hydrate decomposition. Another, previously unknown regime of the self-preservation exists below this temperature, extending however only over a rather narrow pressure range. In this case, the initial ice microstructure is dominated by a fast two-dimensional growth covering rapidly the clathrate surface. All observations lend strong support to the idea that the phenomenon of self-preservation is linked to the permeability of the ice cover governed by (1) the initial microstructure of ice and/or (2) the subsequent annealing of this ice coating. The interplay of the microstructure of newly formed ice and its annealing with the ongoing decomposition reaction leads to various decomposition paths and under certain conditions to a very pronounced preservation anomaly."],["dc.identifier.doi","10.1021/jp906859a"],["dc.identifier.isi","000272083000010"],["dc.identifier.pmid","19904911"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/55699"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Chemical Soc"],["dc.relation.issn","1520-6106"],["dc.title","\"Self-Preservation\" of CO2 Gas Hydrates-Surface Microstructure and Ice Perfection"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]